Jack was last employed by the cyber security consulting firm IOActive Inc, and specialized in embeddable devices (like the computers one finds in ATMs or medical devices). Jack worked as a white-hat hacker, looking for flaws in systems so that they could be fixed. One of his earlier exploits was finding a flaw in insulin pumps that made it possible for someone to remotely deliver fatal doses of insulin. He also, famously, found a vulnerability in ATMs that made them spit out money, as seen in the video above. By figuring out how to exploit these systems, Jack provided information that companies needed to make their products more secure.